Analog of haemophilus Hin47 with reduced protease activity

Abstract

An isolated and purified analog of Haemophilus influenzae Hin47 protein has a decreased protease activity which is less than about 10% of that of natural Hin47 protein and preferably substantially the same immunogenic properties as natural Hin47 protein. An isolated an purified nucleic acid molecule encoding the Hin47 analog may be provided in a recombinant plasmid which may be introduced into a cell which is grown to produce the Hin47 analog. Immunogenic compositions comprising the Hin47 analog and the encoding nucleic acid may be formulated as vaccines for in vivo administration to a host, including a human, to confer protection against diseases caused by a bacterial pathogen, including Haemophilus species, such as Haemophilus influenzae, that produces Hin47 protein or a protein capable of inducing antibodies in the host specifically reactive with Hin47 protein. The Hin47 analog and the encoding nucleic acid also may be employed in diagnostic applications.

Description

The present invention relates to the field of immunology and is particularly concerned with immunogens and antigens from species of Haemophilus.BACKGROUND TO THE INVENTIONHaemophilus influenzae is the organism responsible for a variety of serious human diseases, such as meningitis, epiglotitis, pneumonia and otitis media. Haemophilus influenzae type b (Hib) is a major cause of bacterial meningitis in children under the age of five years. Protective antibodies to the disease are induced by the capsular polysaccharide of the organism and vaccines have been developed that utilise the purified polyribosyl ribitol phosphate (PRP) as the antigen. This vaccine provides 90% protection in adults and in children over 24 months of age, but was ineffective in children under 24 months (Zangwill et al 1993). (The references are identified in a list of references at the end of this disclosure, each of which reference in the list is hereby incorporated by reference without further reference thereto...

AI Technical Summary

Benefits of technology

Referring to FIG. 8, there is illustrated an analysis of the increased stability of an analog of Hin47 as provided herein. Thus, in one embodiment of the present invention, there is provided an analog of Hin47 protein having increased thermal stability, and such analog may specifically have amino acid serine-197 replaced by alanine.

Accordingly, the present invention provides the primary sequence and the preparation of analogs of Hin47 of H. influenzae that can be used in the prevention and diagnosis of diseases caused by H. influenzae In particular, the inventors discovered that the Hin47 analogs can elicit protective immune responses against live H. influenzae type b bacterial challenge. Thus, the present inventions have utility in vaccines. The invention also discloses the nucleotide sequences of the genes encoding the Hin47 analogs. These DNA segments may be used to provide an immunogen essentially free from other H. influenzae antigens, such as PRP and lipooligosaccharides (LOS), through the application of recombinant DNA technology. The Hin47 analog protein, may be produced in a suitable expression system, such as E. coli, Haemophilus, Bacillus, Bordetella Fungi, Yeast, Baculovirus, Poxvirus, vaccinia or mammalian expression systems. The present disclosure further provides novel techniques which can be employed for preparing essentially pure Hin47 analogs.

The Hin47 analogs of the present invention are useful as immunogens for the generation of anti-Hin47 antibodies, as antigens in immunoassays including enzyme-linked immunosorbent assays (ELISA), RIAs and other non-enzyme linked antibody binding assays or procedures known in the art for the detection of anti-bacterial, Haemophilus, and anti-Hin47 antibodies. In ELISA assays, the Hin47 analogs, are immobilized onto a selected surface, for example, a surface capable of binding proteins such as the wells of a polystyrene microtiter plate. After washing to remove incompletely adsorbed Hin47 analogs, a nonspecific protein such as a solution of bovine serum albumin (BSA) that is known to be antigenically neutral with regard to the test sample may be bound to the selected surface. This allows for blocking of nonspecific adsorption sites on the immobilizing surface and thus reduces the background caused by nonspecific bindings of antisera onto the surface.

The nucleic acid molecules having the sequence encoding the Hin47. analog of the present invention are useful for their ability to selectively form duplex molecules with complementary stretches of other hin47 genes. Depending on the application, a variety of hybridization conditions may be employed to achieve varying degrees of selectivity of the probe toward the other hin47 genes. For a high degree of selectivity, relatively stringent conditions are used to form the duplexes, such as low salt and / or high temperature conditions, such as provided by 0.02 M to 0.15 M NaCl at temperatures of between about 50.degree. to 70.degree. C. For some applications, less stringent hybridization conditions are required, such as 0.15 M to 0.9 M salt, at temperatures ranging from between about 20.degree. C. to 55.degree. C. Hybridization conditions can also be rendered more stringent by the addition of increasing amounts of formamide, to destabilize the hybrid duplex. Thus, particular hybridization conditions can be readily manipulated, and will generally be a method of choice depending on the desired results.

Problems solved by technology

This vaccine provides 90% protection in adults and in children over 24 months of age, but was ineffective in children under 24 months (Zangwill et al 1993).

Like other polysaccharide antigens, PRP does not induce the proliferation of T-helper cells, and reimmunisation fails to elicit either a booster response or an increase in memory cells.

The current Haemophilus conjugate vaccines do not protect against other invasive typable strains (types a and c) and, importantly, do not protect against non-typable (NTHi) strains which are a common cause of postpartum and neonatal sepsis, pneumonia and otitis media.

Chronic otitis media can lead to hearing, speech, and cognitive impairment in children.

A disadvantage of Hin47 for use as an antigen in diagnosis, for the generation of anti-Hin47 antibodies useful in diagnosis and as an immunogen in vaccination is the unexpected discovery by the present applicants that Hin47 has protease activity which results in the autodigestion of Hin47 and the proteolytic degradation of other antigens mixed therewith.

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